1. Field of the Invention
The present invention relates to an image display apparatus capable of selectively increasing or reducing the viewing angle, and an electronic apparatus using the image display apparatus.
2. Description of the Related Art
FIG. 16 shows the structure of an example of a liquid crystal display, designated by H. The liquid crystal display H has a liquid crystal 3 in a twisted nematic (TN) mode interposed between a pair of substrates 1 and 2 facing each other, and polarizing plates 4 and 5 disposed outside the substrates 1 and 2. If the liquid crystal display H is of a thin film transistor type, it is arranged to enable orientation control of the liquid crystal 3 as described below. A source wiring 6 and a gate wiring 7 are provided in a matrix form on one substrate 1. A thin film transistor 8 and a pixel electrodes are provided in a region corresponding to each of intersections of the source wiring 6 and the gate wiring 7. A color filter 10 and a common electrode 11 are provided on the other substrate 2. A potential difference is created between the pixel electrode 9 in each region and the common electrode 11 opposed to the pixel electrode 9 to apply the desired electric field to the liquid crystal 3 between the two electrodes.
In this type of liquid crystal display H, for orientation control of liquid crystal molecules when no electric field is applied, alignment films (not shown) are respectively provided on the pair of substrates 1 and 2 on the liquid crystal sides of the same. The alignment film on the substrate 1 placed under the substrate 2 as viewed in FIG. 16 is rubbed in the direction of arrow B shown in FIG. 17 while the alignment film on the substrate 2 is rubbed in the direction of arrow A shown in FIG. 17.
In the liquid crystal display H having the structure shown in FIG. 16, therefore, liquid crystal molecules homogeneously oriented parallel to the upper and lower substrates 1 and 2 have a twist of 90.degree. between the substrates 1 and 2 when no electric field is applied to the liquid crystal 3. When an electric field is applied to the liquid crystal 3, the liquid crystal molecules are oriented along the direction of the electric field perpendicularly to the substrates. Passage or stoppage of light from a backlight provided under the lower substrate 1 is selected by changing the liquid crystal in this manner, thus enabling the display to be changed between a bright state and a dark state.
Recently, viewing angle dependence of TN liquid crystal display devices of this kind has been taken into consideration. FIG. 18 shows an ordinary viewing angle dependence of a TN mode liquid crystal display. The hatched area in FIG. 18 represents a display area where the contrast ratio (CR) is 10 or higher. As can be clearly understood from FIG. 18, the visibility of the TN mode liquid crystal display is not low when the display is viewed at an angle along the horizontal direction but the visibility is considerably low when the display is viewed at an angle along the vertical direction, particularly at an angle from a higher position.
Under these circumstances, various structures for increasing the liquid crystal viewing angle have been proposed.
As a conventional technique for increasing the viewing angle of a liquid crystal display device of the above-described kind, an orientation division structure for divided orientation of the pixel unit is known. In this orientation division structure, domains where liquid crystal molecules rise in different directions when a voltage is applied are formed in each of pixel regions. Ordinarily, in this kind of structure, each pixel is divided into two and orientation is performed in different manners with respect to the divided two pixel regions. This orientation division structure has reduced and symmetrized steep changes in contrast in TN mode liquid crystal displays, which are considerably large and are exhibited asymmetrically about an angle along the vertical direction. An effect of increasing the area free from half tone gradation reversal has been achieved thereby, which substantiates the possibility that a liquid crystal display having a sufficiently wide viewing angle will be provided.
The inventors of the present invention have achieved the present invention noticing that, in some case, it is preferable to reduce the viewing angle of a liquid crystal display, and that, in some other case, it is preferable to increase the viewing angle of the liquid crystal display.